```erlang
    %% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-
    
    %% ex: ts=4 sw=4 ft=erlang et
    
    ExtraDeps = [{retest, ".*", {git, "git://github.com/dizzyd/retest.git"}}],
    
    case os:getenv("REBAR_EXTRA_DEPS") of
    false ->
    CONFIG;
    _ ->
    case lists:keysearch(deps, 1, CONFIG) of
    {value, {deps, Deps}} ->
    NDeps = Deps ++ ExtraDeps,
    lists:keyreplace(deps, 1, CONFIG, {deps, NDeps});
    false ->
    CONFIG ++ [{deps, ExtraDeps}]
    end
    end.
```